In this study, we newly identified or established several isolates or strains of quasi-Otsu-SSUrDNA-type (Nagano SSUrDNA-type) and US-SSUrDNA-type Babesia microti in addition to Kobe-SSUrDNA-type and Otsu-SSUrDNA-type of B. microti from Japanese rodents. Nagano-SSUrDNA-type B. microti was exclusively identified in Eothenomys andersoni, while Otsu-SSUrDNA-type B. microti was identified in Apodemus species in Nagano, where quasi-Otsu-and Otsu-SSUrDNA-type B. microti are endemic. We also identified or established isolates or strains of Kobe-SSUrDNA-type B. microti (the Meishan isolate) from Taiwanese rodents.For these isolates or strains plus the Gl, the N/A, the Kobe, the Otsu and the Hachimaki strains, which had been previously established, the sequences of ITS1/ITS2 were investigated. The percent identities of ITS1/ITS2 between the different SSUrDNA-types were around 50-60%. Within the Otsu-SSUrDNA-type, the ITS1 and ITS2 sequences of all B. microti isolates were different only by 1-3
… Morenucleotides from each other. For the Kobe-SSUrDNA-type of B. microti, all of the isolates from Japanese rodents possessed completely identical ITS1/1TS2 sequences. However, between the Kobe and Meishan strains, around 92% identities were showed. For the US-SSUrDNA-type of B.microti, the ITS sequences of the GI and N/A strains were completely identical, while the ITS1/ITS2 sequence of the Japanese isolate was clearly differentiated from those of the GI and N/A strains with the 91.1 %-97.2% identities.The main immunoreactive antigens of the Kobe and Otsu strains were examined by immunoblot analysis and were shown to be approximately 42kD and 35kD, respectively. Between the same SSUrDNA-type B. microti with different ITS1/ITS2 sequences, the molecular weights of main immunoreactive antigens seemed to be somewhat different, although indirect fluorescent antibody test showed cross immunoreactivities between the same SSUrDNA-type B. microti with different ITS1/ITS2 sequences. Because we could not clone the main immunoreactive antigens, more detailed structural analysis for immunoreactive antigens of the isolates or strains was impossible. Less